[Sathimas]

to get things a bit more clear:
 
At the moment, my amp is wired exactly as cavalli shows  for the "alternate wiring scheme".
 
 
Today the parts for the GLB arrived.
 
 
 

I had a close look at your first image (post # 1552) and it seems correct to me, except that the pot
is not connected. Both channels of the pot have to be connected with their ground pins to ground
or there will be hum!

 
The two ground-pins of the pot are connected with a piece of wired, bridged, so to say.
The ground of the input jacks is also wired to those pins, as well as each "IG" is connected.

 

You seem to have wired all psu grounds and heater grounds to star ground.

 
Yes
 

Amp board and psu board are connected.

Yes
 

RCA's (isolated) and the pot are connected to Star Ground as well as the
output jack. Doing so should result in no hum...?

Output jack is connected to star ground.
 
Ground of the RCAs (which is wired to the pots ground pins) is only connected
to "IG", not to star ground.
 
May that be the problem?

 

[stixx]

  Ground of the RCAs (which is wired to the pots ground pins) is only connected
to "IG", not to star ground.

No, that shouldn't be a problem... According to the wiring scheme that is your Input Ground (IG) which is grounded to the Star through the board.
I usually wire the RCA's and the pot (and sometimes the output jack) as a sub-group that is then connected to the Star Ground. Just make sure
none of your components has two connections to the Star or you will have a Ground Loop.
 
Tricky thing you have there...

 

 

[jdkJake]

At this point, I think you need to consider isolating each channel separately and see if you can narrow things down a bit.

By that, I mean electronically disconnect one channel and see if both channels exhibit the hum independently. Even if they do, it should be easier, at least in theory, to isolate what may be causing the hum.

 

[Sathimas]

First, some more precise discription of the 2disturbing nioses:
 
1. hum
quiet, just hearable - not disturbing anymore when music is playing.
equally loud on both channels, even there with grounded inputs and not changing
with the volume
 
2. crackling, hissing sounds
louder than the hum and increasing with volume
 
 
 
Some update on my results:
 
What I tried up 'til now:
 
1. alternate wiring scheme, but having the GLB between Starground and mains ground
 
- no effect
 
2. alternate wiring scheme, with GLB between star- and mainsground, but having starground
floating and not connected to chassis
 
- no effect
 
3. ground of amp ps and amp directly connected, ground of heater ps not connected
just SG connected to starground, GLB between star- and mainsground
 
- loud hum on left channel, quiet hum (just like before) on the right
 
 
No I'll go on and check the channels one by one.

 

[Sathimas]

right channel only, all wires disconnected from the left one
 
Inputs are open
 
1. 
ground of amp ps and amp directly connected, ground of heater ps not connected
just SG connected to starground, GLB between star- and mainsground
 
- no effect, still having the subtle hum
 
2. 
ground of amp ps and amp directly connected, ground of heater ps and 
SG connected to starground, GLB between star- and mainsground
 
- no noticalbe hum, hum only comes up when I turn up the volume a lot,
much more than I ever would when listening to music
 
- this is the first really positive result
 
no further tests, since the right channel is working as it should now
 
 
Let's move on to the left one, same as before, right channel completely disconnected
 
 
1.
ground of amp ps and amp directly connected, ground of heater ps and 
SG connected to starground, GLB between star- and mainsground
 
- same as left channel! 
- no noticalbe hum, hum only comes up when I turn up the volume a lot,
much more than I ever would when listening to music
 
 
So, let's hook up both channels this way and see what happens:
 
1. - both channels
ground of amp ps and amp directly connected, ground of heater ps and 
SG connected to starground, GLB between star- and mainsground
 
- loud hum on the left, more quiet, but noticable hum on the right
 
 
 
Does this give one you a clou how to solve that problem?

 

[fishski13]

maybe we don't need another cook in the kitchen...

-when you say that the inputs are "open", do you mean that they are NOT shorted to input ground? i would make sure that they are shorted to input ground to rule out that the input wiring from RCA to pot and pot to board inputs is not picking up noise, and that it's the amp itself generating the noise. the input wiring is a high impedance circuit and prone to noise. IME, shielding the input wiring isn't effective for EMI, only RFI. also, make sure the shields are tied to signal/input ground and not chassis ground.

-i see the GLB breaker as been disscused in detail. just make surre all ground points connect to one side of the GLB and the other side of the GLB to chassis ground. not that i think a GLB is your problem.

i had an EHHA here for a rebuild and new chassis. it was basically dead quiet when i received it. when i put it in a larger chassis, with cleaner layout and wiring, i got noise in only one channel. i ended up flipping boards around and routing the wire under the boards a little differently and the noise went away. i don't know if you've tried this, but "chop-sticking"/moving exposed wires can be beneficial in sleuthing out noise as well, especially with input wiring.

 

[newbienewbie]

Hi guys,
 
just today I've managed to resurrect this build from the attic where
it stood for more than half a year. Anyway I've completed all the wiring
hooked it up to a CD player as source and - no sound. Dead quiet nothingness.
No hum no buzz no noise. All the test diodes are lit. I've measured the output
accross the testpoints on the boad and I get about 210mv (the same for both channels),
which is in line with the instructions. Any hints about where I might start the debugging process?
Everything looks ok, soldering seems to have been done ok, no parts look burnt or blown...
 
I'd appreciate a nudge in the right direction.

 

[newbienewbie]

Hey,
 
please just disregard the post above. It turned out to be an issue with the volume pot.
Problem solved.

 

[jdkJake]

right channel only, all wires disconnected from the left one

Inputs are open

1. 
ground of amp ps and amp directly connected, ground of heater ps not connected
just SG connected to starground, GLB between star- and mainsground

- no effect, still having the subtle hum

2. 
ground of amp ps and amp directly connected, ground of heater ps and 
SG connected to starground, GLB between star- and mainsground

- no noticalbe hum, hum only comes up when I turn up the volume a lot,
much more than I ever would when listening to music

- this is the first really positive result

no further tests, since the right channel is working as it should now


Let's move on to the left one, same as before, right channel completely disconnected


1.
ground of amp ps and amp directly connected, ground of heater ps and 
SG connected to starground, GLB between star- and mainsground

- same as left channel! 
- no noticalbe hum, hum only comes up when I turn up the volume a lot,
much more than I ever would when listening to music


So, let's hook up both channels this way and see what happens:

1. - both channels
ground of amp ps and amp directly connected, ground of heater ps and 
SG connected to starground, GLB between star- and mainsground

- loud hum on the left, more quiet, but noticable hum on the right



Does this give one you a clou how to solve that problem?

Interesting.

Do you have the left and right signal grounds tied together at the inputs? If not, are they tied together at the pot?

 

[Sathimas]

 -when you say that the inputs are "open", do you mean that they are NOT shorted to input ground? i would make sure that they are shorted to input ground to rule out that the input wiring from RCA to pot and pot to board inputs is not picking up noise, and that it's the amp itself generating the noise.

 
Inputs were not grounded - but even with open inputs each channel for itself was quiet.
 
When I have both channels operating the loud hum on the left is there
with and without grounded inputs - so the hum must be coming from the amp itself.
 

 Do you have the left and right signal grounds tied together at the inputs? If not, are they tied together at the pot?

 
Input ground wiring:
 
All 4 input groundconncectors are connected in line
From there input ground is wired to the pot (ground pins of the pot
connected as well) From the pot input ground is wired to IG on the board.

 

[Sathimas]

Some more experimenting (inputs grounded)
 
Changes:
 
1. headphone-jack ground wired to both groundconnectors on the amp boards
 
- less (next to no) hum on the right, small decrease in hum volume on the left, but still loud
 
2. Trying asymmetrical wiring: (leaving jack-gr connected to amp-gr)
 
- right channel - ps-gr tied to amp-gr
- left channel - ps-gr tied to star-gr
 
-> no hum on the right, even when turning up the volume very high
-> slight hum on the left, but still noticable (not changing with volume)
 
We'll  - I'm getting closer !
 
 
The hissing/buzzing is also gone when connected to my y1-DAC.

 

[fishski13]

just for clarity, what i mean by "inputs shorted" is: the pot not connected to amp boards and each input pad connected to input ground on each board connected with a wire lead snipping or wire. if the pot is connected, you have not isolated the pot as the problem.

i'm not sure if you're doing this, but keep all grounds from each channel completely separate up to the GLB/star ground. i.e. L/R channel grounds only meet at one point at the star ground.

 

[jdkJake]

Input ground wiring:

All 4 input groundconncectors are connected in line
From there input ground is wired to the pot (ground pins of the pot
connected as well) From the pot input ground is wired to IG on the board.

I think you should do what fishski13 is recommending and take the entire input section, including the pot, out of the equation and see where things lie.

I am a fan of wiring input signal grounds to the pot sperately and maintaining them separately all the way into the input(s) of the amp boards. I think you should separate those input grounds after you try what fishski13 recommends to see if the input section is the cause of the problem. His recommended test is straightforward and should answer a few concerns I see with your input wiring.

 

[Sathimas]

Inputs were grounded at the input jacks.
 
I'll try your suggestions tomorrow and see what happens.

 

[fishski13]

Noise is really frustrating, especially after you spent all the work you put into the chassis and layout. I think you're really close.

As Jake said, i too prefer to keep the L/R grounds separate from input RCAs through the pot and to the boards. With star grounding, it's best to keep the channel grounds separate from one another up to the chassis star ground.